130 Pub. Puget Sound Biol. Sta. Vol. 2, No. 42 



June to August. The eggs are beautifully clear; the bilateral cleavage 

 may be perfectly followed in the living eggs. This is one of the best 

 forms for the study of cleavage. The whole development may be followed 

 in 3 or 4 days, and the young may be obtained by towing. 



Pleurobrachia sp. Common thruout the season in Friday Harbor, and 

 obtainable from the Station floats. These were not as abundant during 

 1918 as in 1917. The eggs are large and clear, and are easily raised in 

 the laboratory. 



Beroe sp. Not as common as Mnemiopsis or Pleurobrachia. These 

 come rather late in the season, July to August. The eggs are smaller than 

 the forms mentioned above. The animal can easily be raised in the lab- 

 oratory. 



Echinodermata 



Orthasterias forreri forcipulata Verrill. Occasionally brought up in 

 the trawl. Ripe eggs and sperms were obtained during the season 1917, 

 and gave normal bipinnaria larvae in the course of four or five days. 



Solaster dawsoni Verrill. Commonly secured by means of the trawl 

 thruout the season. Eggs and motile sperms may be obtained. Specimens 

 taken July 15, 1918, showed immature ova. 



Evasterias troschelii (Stimpson) Verrill. Common in hauls of the 

 trawl and occasionally found along the shore. They carry eggs and motile 

 sperms, June to August. 



Ophiura brevispina Say. Abundant in certain localities in hauls of 

 the trawl. Eggs are present, but the sperms are only in part motile. They 

 may have a fall reproductive season. 



Amphioplus abditus Verrill. Occasional under rocks at low tide from 

 Minnesota Reef to Argyle Bay. The eggs were ripe but the sperms were 

 only in part motile. They may have a fall reproductive period. 



Gorgonocephalus eucnemis Miiller & Troschel. Occasionally secured 

 with the trawl. The gonads are turgid with heavy yolk-filled eggs. The 

 sperms are in part motile. They may have a fall reproductive period. 



Strong ylocentrotus drobachiensis O. F. Miiller. A very abundant 

 form obtained along shore and in shallow trawling. Occasionally individ- 

 uals will be found to contain ripe eggs or sperms late in June or early in 

 July, but for the most part the gonads are spent, and regressive changes 

 are going on. 



Strong ylocentrotus franciscanus A. Agassiz. Abundant along shal- 

 low water from Pt. Caution to Turn Island. The season is evidently earlier 

 than June, when the Station opens. Occasionally during June, July, and 

 August individuals will be found containing ripe eggs or sperms. During 

 July 1917 this urchin yielded material in abundance, but this was not so 

 in 1918, when it was exceptional to find specimens with ripe reproductive 



